The DCT shouldn't be affected by wheel/tire variations from factory sizes - the computer is watching speed (probably measured inside the transmission) and RPM to select the next gear. And whether the speed is accurate or not wont make a difference to the DCT, but it might to the rider as it could result in speedometer error.Is yours normal or DCT i was wondering to get tubeless tyres, but I'm waiting for a DCT, and i did think the ecu and transmission might flipout due to different rolling radius ??
ABS and traction control could be affected - it will depend on your tire size choices. At the rear, the OEM tire is a 150/70-18 with a (calculated) diameter of 26.6 inches and at the front with a 90/90-21 and a diameter of 28.3 inches you end up with a ratio of 1:1.07. If you can stay near that ratio with 17 and 19 inch wheels/tires (say with a 110/80-19 - 26.2" front and rear 170/60-17 - 25.3" with a ratio of 1:1.05) that might be close enough for the computer to manage without going crazy. (Assumes there is room between the swingarm sides for a 170mm wide tire.)
I calculate tire diameter by computing the height of the tire by multiplying the width by the aspect ratio (150 x 0.7 = 105mm) then converting to inches (105/24.5 =4.3") times 2 = 8.6 plus the wheel size 18" += 26.6 inches. Actual tire diameter will vary somewhat between manufacturers, tread style, street or dirt, etc.
As for benefits/disadvantages - 17/19" sizes will only lower the bike by one half the measured diameter (about an inch) and you can usually do a lot better than that with lowering links and dropping the triple clamps down on the fork tubes - at a much lower cost than changing wheel sizes and tires. You will have a greater selection of tires (TT and TL) with 17/19's.
As for me, I'm inclined to agree with True Ad Venture: look at the NC models (if you can deal with 50 HP). Or wait for Honda to bring out street oriented variations of the Africa Twin the way Yamaha has done with it's brilliant FZ/MT-FJ/XSR/MWT family.